23 results on '"Guojin Zhang"'
Search Results
2. Author response for 'Self‐optimization for smelting process of fused magnesium furnace based on operation status assessment'
- Author
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Guojin Zhang, Mingxing Jia, and Dapeng Niu
- Subjects
Status assessment ,chemistry ,business.industry ,Magnesium ,Environmental science ,chemistry.chemical_element ,Smelting process ,Process engineering ,business ,Self-optimization - Published
- 2021
3. An Amine-Borane System Featuring Room-Temperature Dehydrogenation and Regeneration
- Author
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Chang Won Yoon, Zhenguo Huang, Guochen Bao, Daniel Morrison, Taek-Yong Song, Haibo Yu, Guojin Zhang, Alison T. Ung, and Jihye Lee
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Materials science ,010405 organic chemistry ,Organic Chemistry ,chemistry.chemical_element ,Boranes ,Ethylenediamine ,General Medicine ,General Chemistry ,Borane ,010402 general chemistry ,01 natural sciences ,Nitrogen ,Catalysis ,0104 chemical sciences ,chemistry.chemical_compound ,Hydrogen storage ,chemistry ,Polymer chemistry ,Amine gas treating ,Dehydrogenation ,03 Chemical Sciences ,Boron - Abstract
Amine-borane complexes have been extensively studied as hydrogen storage materials. Herein, we report a new amine-borane system featuring a reversible dehydrogenation and regeneration at room temperature. In addition to high purity H2 , the reaction between ethylenediamine bisborane (EDAB) and ethylenediamine (ED) leads to unique boron-carbon-nitrogen 5-membered rings in the dehydrogenation product where one boron is tricoordinated by three nitrogen atoms. Owing to the unique cyclic structure, the dehydrogenation product can be efficiently converted back to EDAB by NaBH4 and H2 O at room temperature. This finding could lead to the discovery of new amine boranes with potential usage as hydrogen storage materials.
- Published
- 2021
4. Investigation of the interactions of cationic guar with human hair by electrokinetic analysis
- Author
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Bert Kroon, Guojin Zhang, Roger L McMullen, and Donna Laura
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Aging ,Cocamidopropyl betaine ,Static Electricity ,Guar ,Hair Preparations ,Pharmaceutical Science ,Dermatology ,030226 pharmacology & pharmacy ,Streaming current ,030207 dermatology & venereal diseases ,03 medical and health sciences ,chemistry.chemical_compound ,Surface-Active Agents ,0302 clinical medicine ,Colloid and Surface Chemistry ,Pulmonary surfactant ,Desorption ,Cations ,Drug Discovery ,Zeta potential ,Carbohydrate Conformation ,Humans ,Mechanical Phenomena ,integumentary system ,Chemistry ,Cationic polymerization ,Cyamopsis ,Shampoo ,Molecular Weight ,Chemical engineering ,Chemistry (miscellaneous) ,Hair - Abstract
Cationic guar is an important polysaccharide used as a hair conditioning agent in personal care products. In this article, we report streaming potential data demonstrating its behaviour as it interacts electrostatically with hair. Several cationic guar variants with different molecular weights (MWs) and charge densities (CDs) were examined.All experiments were carried out with a custom-designed streaming potential instrument so that in situ, real-time data were monitored during the treatment of a hair plug with aqueous solutions of cationic guar and subsequent treatment with anionic surfactants-sodium laureth sulfate (SLES) and cocamidopropyl betaine (CAPB)-commonly found in contemporary shampoo formulations.The MW of the cationic guar variants plays an integral role in determining the thickness of the adsorbed polymer layer on the hair surface while CD influences the zeta potential. Data were also generated for the treatment of hair with a cationic flexible polymer (polyquaternium-28) and cationic conditioning surfactant (behentrimonium chloride) to provide a frame of reference. The deposition behaviour on hair of high MW cationic guar variants is distinct from these conventional molecules in terms of its electrokinetic properties. We also examined the electrokinetic behaviour of cationic guar on hair types from different racial backgrounds. While the cationic guar treatment yielded similar results for the different hair types, anionic surfactant treatment resulted in quicker sorption and desorption from African, European 65% grey, and Mulatto hair as compared to Chinese, European dark brown, and Indian hair.We introduce an in situ technique for measuring the dynamic sorption/desorption of charged molecules on the surface of human hair. Evaluation of a series of cationic guar species revealed varying behaviour depending on the MW and CD of the polysaccharide. Our data also demonstrate differences in the desorption properties of typical shampoo surfactants for hair from diverse racial backgrounds.Le guar cationique est un polysaccharide important utilisé comme conditionneur capillaire dans les produits cosmétiques. Dans ce rapport, nous démontrons l'utilisation de la technique du potentiel de streaming pour étudier comment le guar cationique interagit électrostatiquement avec les cheveux. Plusieurs variantes del guar cationique avec différents poids moléculaires et densités de charge ont été examinés. MÉTHODES: Nous avons utilisé un instrument de potentiel de streaming pour les expériences. Les études ont été réalisées en temps réel pour surveiller le traitement de cheveu avec des solutions aqueuses de guar cationique suivi d'un traitement ultérieur avec tensioactifs anioniques comment le sulfate de laureth de sodium et le cocamidopropyle bétaïne, des ingrédients généralement trouvés dans les formulations de shampooing. RÉSULTATS: Le poids moléculaire des variants du guar cationique joue un rôle intégral dans la détermination l'épaisseur de la couche de polymère adsorbée sur la surface des cheveux tandis que le densité de charge influence le potentiel zêta. Des données ont également été générées pour le traitement des cheveux avec un polymère flexible (polyquaternium-28) et tensioactif de conditionnement cationique (behentrimonium chlorure) pour fournir un cadre de référence. Le comportement de dépôt sur les cheveux des variants de guar cationiques à poids moléculaire élevé est distinct de ces molécules conventionnelles en termes de ses propriétés électrocinétiques. Nous avons également examiné le comportement électrocinétique de guar cationique sur des types de cheveux de différents milieux raciaux. Le traitement avec le guar cationique a donné des résultats similaires pour les différents types de cheveux. En contraste avec ceci, le traitement avec le tensioactif anionique a entraîné une sorption et une désorption plus rapides de cheveux africains, de cheveux européens (65% gris) et de cheveux mulâtres en comparaison à les cheveux chinois, européens et indiens.Nous introduisons une technique in situ pour mesurer la sorption et la désorption dynamique de molécules chargées à la surface des cheveux humains. L’évaluation d'une série des espèces de guar cationiques ont révélé un comportement variable en fonction du poids moléculaires et densités de charge de le polysaccharide. Nos données démontrent également des différences dans les propriétés de désorption de tensioactifs de shampooing typiques pour les cheveux de diverses origines raciales.
- Published
- 2021
5. Polyaniline nanowires on Si surfaces fabricated with DNA templates
- Author
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Yufeng Ma, Jianming Zhang, Guojin Zhang, and Huixin He
- Subjects
DNA -- Research ,Silicon -- Chemical properties ,Aniline -- Chemical properties ,Chemistry - Abstract
The fabrication of conducting polymer nanowires on thermally oxidized Si surfaces by use of DNA templates is described. The conductivity of the nanowires is very sensitive to the proton doping-undoping process, suggesting that the nanowires hold great promise for sensitive chemical sensor applications.
- Published
- 2004
6. Palladium-catalyzed synthesis of 8-allyl or 8-prenylcoumarins by using organotin reagents as multicoupling nucleophiles
- Author
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Qiang Yin, Weihua Zhang, Yaqin Zhang, Guojin Zhang, Yige Wang, Han Yan, and Yuxiang He
- Subjects
Inorganic Chemistry ,Nucleophile ,chemistry ,Reagent ,Organic chemistry ,chemistry.chemical_element ,General Chemistry ,Stille reaction ,Catalysis ,Palladium - Abstract
In this study, 8-iodocoumarin derivatives underwent a direct Stille cross-coupling reaction with several organotin compounds in the presence of a catalytic amount of Pd(PPh3)4 in DMF at 80 °C. The cross-coupling reaction proceeded smoothly under mild conditions and permitted the formation of 8-allyl or 8-prenylcoumarin compounds in good yields. Copyright © 2012 John Wiley & Sons, Ltd.
- Published
- 2012
7. Raman microspectroscopic and dynamic vapor sorption characterization of hydration in collagen and dermal tissue
- Author
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K. L. Andrew Chan, Guojin Zhang, Carol R. Flach, Qihong Zhang, Timothy Gillece, Laurence Senak, Richard Mendelsohn, and David J. Moore
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Protein Conformation ,Swine ,Biopsy ,Biophysics ,Analytical chemistry ,Spectrum Analysis, Raman ,Biochemistry ,Collagen Type I ,Biomaterials ,symbols.namesake ,Dermis ,medicine ,Animals ,Humans ,Deuterium Oxide ,Microscopy, Confocal ,Chemistry ,Hydrogen bond ,Organic Chemistry ,Intermolecular force ,technology, industry, and agriculture ,Water ,Humidity ,Hydrogen Bonding ,General Medicine ,medicine.anatomical_structure ,Models, Chemical ,Deuterium ,symbols ,Adsorption ,Collagen ,Dynamic vapor sorption ,Raman spectroscopy ,Wound healing ,Type I collagen - Abstract
Water is an integral part of collagen's triple helical and higher order structure. Studies of model triple helical peptides have revealed the presence of repetitive intrachain, interchain, and intermolecular water bridges (Bella et al., Structure 1995, 15, 893-906). In addition, an extended cylinder of hydration is thought to be responsible for collagen fiber assembly. Confocal Raman spectroscopy and dynamic vapor sorption (DVS) measurements of human Type I collagen and pigskin dermis were performed to probe relative humidity (RH)-dependent differences in the nature and level of collagen hydration. Raman spectra were also acquired as a function of time for both Type I collagen and pigskin dermis samples upon exchange of a 100% RH H(2) O to deuterium oxide (D(2) O) environment. Alterations in Amide I and III modes were consistent with anticipated changes in hydrogen bonding strength as RH increased and upon H → D exchange. Of note is the identification of a Raman spectral marker (band at 938 cm(-1) ) which appears to be sensitive to alterations in collagen-bound water. Analysis of DVS isotherms provided a quantitative measure of adsorbed and absorbed water vapor consistent with the Raman results. The development of a Raman spectral marker of collagen hydration in intact tissue is relevant to diverse fields of study ranging from the evaluation of therapeutics for wound healing to hydration of aging skin.
- Published
- 2011
8. A coordinated approach to cutaneous wound healing: vibrational microscopy and molecular biology
- Author
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Carol R. Flach, K. L. Andrew Chan, Marjana Tomic-Canic, Richard Mendelsohn, Brian Lee, Guojin Zhang, and Olivera Stojadinovic
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Pathology ,Indoles ,Time Factors ,confocal Raman microscopy ,Spectrophotometry, Infrared ,wound healing ,Human skin ,Spectrum Analysis, Raman ,Protein-Lysine 6-Oxidase ,030207 dermatology & venereal diseases ,0302 clinical medicine ,Skin Physiological Phenomena ,Keratin ,Microscopy ,Skin ,chemistry.chemical_classification ,0303 health sciences ,integumentary system ,biology ,Immunohistochemistry ,3. Good health ,Matrix Metalloproteinase 7 ,Molecular Medicine ,migrating epithelial tongue ,Collagen ,Cutaneous wound ,DNA microarray ,Adult ,medicine.medical_specialty ,Confocal ,Protein Array Analysis ,03 medical and health sciences ,Organ Culture Techniques ,medicine ,Humans ,Molecular Biology ,Fluorescent Dyes ,030304 developmental biology ,infrared imaging ,Reproducibility of Results ,Cell Biology ,Cathepsins ,Perspective..... Human Skin Wound Healing ,chemistry ,Images in Cellular/Molecular Medicine ,biology.protein ,Biophysics ,Wound healing ,Elastin - Abstract
The repair of cutaneous wounds in the adult body involves a complex series of spatially and temporally organized processes to prevent infection and restore homeostasis. Three characteristic phases of wound repair (inflammation, proliferation including re-epithelialization and remodelling) overlap in time and space. We have utilized a human skin wound-healing model to correlate changes in genotype and pheno-type with infrared (IR) and confocal Raman spectroscopic images during the re-epithelialization of excisional wounds. The experimental protocols validated as IR images clearly delineate the keratin-rich migrating epithelial tongue from the collagen-rich wound bed. Multivariate statistical analysis of IR datasets acquired 6 days post-wounding reveal subtle spectral differences that map to distinct spatial distributions, which are correlated with immunofluorescent staining patterns of different keratin types. Images computed within collagen-rich regions expose complementary spatial patterns and identify elastin in the wound bed. The temporal sequence of events is explored through a comparison of gene array analysis with confocal Raman microscopy. Our approach demonstrates the feasibility of acquiring detailed molecular structure information from the various proteins and their subclasses involved in the wound-healing process.
- Published
- 2008
9. Tracking the dephosphorylation of resveratrol triphosphate in skin by confocal Raman microscopy
- Author
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Carol R. Flach, Richard Mendelsohn, and Guojin Zhang
- Subjects
Time Factors ,Antioxidant ,endocrine system diseases ,Swine ,Chemistry, Pharmaceutical ,Drug Compounding ,Skin Absorption ,medicine.medical_treatment ,Biological Availability ,Pharmaceutical Science ,Resveratrol ,Administration, Cutaneous ,Spectrum Analysis, Raman ,Article ,Antioxidants ,Permeability ,law.invention ,Dephosphorylation ,chemistry.chemical_compound ,Confocal microscopy ,law ,Stilbenes ,Stratum corneum ,medicine ,Animals ,Prodrugs ,Phosphorylation ,skin and connective tissue diseases ,Skin ,chemistry.chemical_classification ,Microscopy, Confocal ,Epidermis (botany) ,Hydrolysis ,organic chemicals ,food and beverages ,Free radical scavenger ,Organophosphates ,Enzyme ,medicine.anatomical_structure ,chemistry ,Biochemistry ,Diffusion Chambers, Culture ,hormones, hormone substitutes, and hormone antagonists - Abstract
Polyphenolic resveratrol has been identified as a potent antioxidant acting as both a free radical scavenger and an inhibitor of enzyme oxidative activity. However, the reactive propensity of resveratrol also limits its use in topical formulations. A transient derivative of resveratrol, resveratrol triphosphate, has been designed to provide a means for the delayed delivery of the active compound in skin tissue where endogenous enzymes capable of dephosphorylation reside. Confocal Raman microscopy studies of intact pigskin biopsies treated with modified resveratrol provided information about the spatial distribution and time-dependence of permeation and conversion to the native active form. Conversion to the active form was not observed when skin samples were exposed to steam, a procedure that likely inactivates endogenous skin enzymes. In addition, treatment with the triphosphate compared to the parent compound revealed a more homogeneous distribution of resveratrol throughout the stratum corneum and viable epidermis when the former was applied. Thus, the bioavailability of resveratrol in the epidermis appears to be enhanced upon application of the pro-molecule compared to resveratrol.
- Published
- 2007
10. ChemInform Abstract: Dual Hypervalent Iodine(III) Reagents and Photoredox Catalysis Enable Decarboxylative Ynonylation under Mild Conditions
- Author
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Hanchu Huang, Yiyun Chen, and Guojin Zhang
- Subjects
Chemistry ,Decarboxylation ,Reagent ,Radical ,Hypervalent molecule ,nutritional and metabolic diseases ,Photoredox catalysis ,chemistry.chemical_element ,General Medicine ,Iodine ,Combinatorial chemistry ,Catalysis - Abstract
The first hypervalent iodine reagent (HIR)/photoredox dual catalysis to form radicals from α-ketoacids, followed by an unprecedented acyl radical addition to HIR-bound alkynes is presented.
- Published
- 2015
11. Dual Hypervalent Iodine(III) Reagents and Photoredox Catalysis Enable Decarboxylative Ynonylation under Mild Conditions
- Author
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Hanchu Huang, Guojin Zhang, and Yiyun Chen
- Subjects
Reaction conditions ,Aqueous solution ,Light ,Chemistry ,Radical ,Acylation ,Receptor, Metabotropic Glutamate 5 ,Hypervalent molecule ,Carboxylic Acids ,Photoredox catalysis ,chemistry.chemical_element ,General Medicine ,General Chemistry ,Ketones ,Photochemistry ,Iodine ,Catalysis ,Reagent ,Alkynes ,Humans ,Indicators and Reagents ,Oxidation-Reduction - Abstract
A combination of hypervalent iodine(III) reagents (HIR) and photoredox catalysis with visible light has enabled chemoselective decarboxylative ynonylation to construct ynones, ynamides, and ynoates. This ynonylation occurs effectively under mild reaction conditions at room temperature and on substrates with various sensitive and reactive functional groups. The reaction represents the first HIR/photoredox dual catalysis to form acyl radicals from α-ketoacids, followed by an unprecedented acyl radical addition to HIR-bound alkynes. Its efficient construction of an mGlu5 receptor inhibitor under neutral aqueous conditions suggests future visible-light-induced biological applications.
- Published
- 2015
12. Applications of Vibrational Spectroscopic Imaging in Personal Care Studies
- Author
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Guojin Zhang, Roger L. McMullen, Richard Mendelsohn, and Osama M. Musa
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medicine.medical_specialty ,Personal care ,Chemistry ,medicine ,Medical physics - Published
- 2015
13. Vibrational Microspectroscopy and Imaging of Molecular Composition and Structure During Human Corneocyte Maturation
- Author
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David J. Moore, Guojin Zhang, Richard Mendelsohn, and Carol R. Flach
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Molecular composition ,Spectrophotometry, Infrared ,Dermatology ,Filaggrin Proteins ,Spectrum Analysis, Raman ,Vibration ,Biochemistry ,symbols.namesake ,Intermediate Filament Proteins ,Microscopy ,Stratum corneum ,medicine ,Humans ,Molecule ,Molecular Biology ,Corneocyte ,Epidermis (botany) ,Chemistry ,Cell Biology ,Lipids ,Exfoliation joint ,medicine.anatomical_structure ,Epidermal Cells ,Biophysics ,symbols ,Epidermis ,Raman spectroscopy - Abstract
The outermost region of the epidermis, the stratum corneum (SC), provides an essential barrier to water loss and protects against exogenous substances. The functional integrity of the SC depends on a complex maturation and exfoliation process, which is often perturbed in skin diseases. The maturation of corneocytes isolated from different depths in healthy human SC was investigated using infrared (IR) spectroscopic imaging and Raman microscopy. Both IR and Raman spectral quality of individual corneocytes was high and revealed depth-dependent variations in molecular composition. Spectral changes were identified as arising from alterations in the concentration of the major constituents of natural moisturizing factor (NMF), important in maintaining SC hydration. A significant decrease in the concentration of NMF was observed for corneocytes isolated from superficial compared to deeper SC layers (layer 3 vs. layer 11, respectively). An IR parameter that measures the relative NMF concentration in corneocytes is introduced. The potential role of vibrational imaging to evaluate corneocyte composition and molecular structure in the treatment of NMF-related diseases is discussed.
- Published
- 2006
14. ChemInform Abstract: Visible-Light-Induced Chemoselective Deboronative Alkynylation under Biomolecule-Compatible Conditions
- Author
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Shuaiyan Zhang, Yiyun Chen, Guojin Zhang, Hanchu Huang, and Li Gong
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chemistry.chemical_classification ,chemistry.chemical_compound ,Quenching (fluorescence) ,Aqueous solution ,chemistry ,Silylation ,Aryl ,Biomolecule ,General Medicine ,Combinatorial chemistry ,Alkyl ,Coupling reaction ,Amino acid - Abstract
Here, we report a visible-light-induced deboronative alkynylation reaction, which is redox-neutral and works with primary, secondary and tertiary alkyl trifluoroborates or boronic acids to generate aryl, alkyl and silyl substituted alkynes. This reaction is highly chemoselective and performs well on substrates containing alkenes, alkynes, aldehydes, ketones, esters, nitriles, azides, aryl halides, alkyl halides, alcohols, and indoles, with no detectable occurrence of side reactions. The mechanism of this novel C(sp(3))-C(sp) bond coupling reaction was investigated by luminescence quenching, radical trapping, on-off light, and C-13-isotopic-labeling experiments. This reaction can be performed in neutral aqueous conditions, and it is compatible with amino acids, nucleosides, oligosaccharides, nucleic acids, proteins, and cell lysates.
- Published
- 2014
15. Visible-light-induced chemoselective deboronative alkynylation under biomolecule-compatible conditions
- Author
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Yiyun Chen, Shuaiyan Zhang, Li Gong, Hanchu Huang, and Guojin Zhang
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chemistry.chemical_classification ,Boron Compounds ,Aqueous solution ,Quenching (fluorescence) ,Silylation ,Light ,Molecular Structure ,Biomolecule ,Aryl ,Glutamic Acid ,General Chemistry ,Biochemistry ,Combinatorial chemistry ,Coupling reaction ,Catalysis ,Amino acid ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,chemistry ,Alkynes ,Organometallic Compounds ,Organic chemistry ,Alkyl - Abstract
Here, we report a visible-light-induced deboronative alkynylation reaction, which is redox-neutral and works with primary, secondary and tertiary alkyl trifluoroborates or boronic acids to generate aryl, alkyl and silyl substituted alkynes. This reaction is highly chemoselective and performs well on substrates containing alkenes, alkynes, aldehydes, ketones, esters, nitriles, azides, aryl halides, alkyl halides, alcohols, and indoles, with no detectable occurrence of side reactions. The mechanism of this novel C(sp(3))-C(sp) bond coupling reaction was investigated by luminescence quenching, radical trapping, on-off light, and (13)C-isotopic-labeling experiments. This reaction can be performed in neutral aqueous conditions, and it is compatible with amino acids, nucleosides, oligosaccharides, nucleic acids, proteins, and cell lysates.
- Published
- 2014
16. Vibrational spectroscopy and microscopic imaging: novel approaches for comparing barrier physical properties in native and human skin equivalents
- Author
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Guojin Zhang, Carol R. Flach, Guo Yu, and Richard Mendelsohn
- Subjects
Spectrophotometry, Infrared ,Swine ,Biomedical Engineering ,Infrared spectroscopy ,Human skin ,Nanotechnology ,Spectrum Analysis, Raman ,Thermotropic crystal ,law.invention ,Biomaterials ,symbols.namesake ,Confocal microscopy ,law ,Skin Physiological Phenomena ,Stratum corneum ,medicine ,Animals ,Humans ,Skin ,Microscopy, Confocal ,integumentary system ,Chemistry ,Temperature ,Lipids ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,medicine.anatomical_structure ,Models, Animal ,Biophysics ,symbols ,Orthorhombic crystal system ,Raman spectroscopy - Abstract
Vibrational spectroscopy and imaging have been used to compare barrier properties in human skin, porcine skin, and two human skin equivalents, Epiderm 200X with an enhanced barrier and Epiderm 200 with a normal barrier. Three structural characterizations were performed. First, chain packing and conformational order were compared in isolated human stratum corneum (SC), isolated porcine SC, and in the Epiderm 200X surface layers. The infrared (IR) spectrum of isolated human SC revealed a large proportion of orthorhombically packed lipid chains at physiological temperatures along with a thermotropic phase transition to a state with hexagonally packed chains. In contrast, the lipid phase at physiological temperatures in both porcine SC and in Epiderm 200X, although dominated by conformationally ordered chains, lacked significant levels of orthorhombic subcell packing. Second, confocal Raman imaging of cholesterol bands showed extensive formation of cholesterol-enriched pockets within the human skin equivalents (HSEs). Finally, IR imaging tracked lipid barrier dimensions as well as the spatial disposition of ordered lipids in human SC and Epiderm 200X. These approaches provide a useful set of experiments for exploring structural differences between excised human skin and HSEs, which in turn may provide a rationale for the functional differences observed among these preparations.
- Published
- 2012
17. Multiscale analysis of water uptake and erosion in biodegradable polyarylates
- Author
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Richard Mendelsohn, Carol R. Flach, Loreto M. Valenzuela, N. Sanjeeva Murthy, Guojin Zhang, Joachim Kohn, and Bozena Michniak-Kohn
- Subjects
chemistry.chemical_classification ,Materials science ,Polymers and Plastics ,Scanning electron microscope ,Analytical chemistry ,Oxide ,Polymer ,Condensed Matter Physics ,Article ,Solvent ,symbols.namesake ,chemistry.chemical_compound ,chemistry ,Deuterium ,Mechanics of Materials ,Materials Chemistry ,symbols ,Porosity ,Raman spectroscopy ,Water content - Abstract
The role of hydration in degradation and erosion of materials, especially biomaterials used in scaffolds and implants, was investigated by studying the distribution of water at length scales from 0.1 nm to 0.1 mm using Raman spectroscopy, small-angle neutron scattering (SANS), Raman confocal imaging, and scanning electron microscopy (SEM). The measurements were demonstrated using L-tyrosine derived polyarylates. Bound- and free- water were characterized using their respective signatures in the Raman spectra. In the presence of deuterium oxide (D(2)O), H-D exchange occurred at the amide carbonyl but was not detected at the ester carbonyl. Water appeared to be present in the polymer even in regions where there was little evidence for N-H to N-D exchange. SANS showed that water is not uniformly dispersed in the polymer matrix. The distribution of water can be described as mass fractals in polymers with low water content (~5 wt%), and surface fractals in polymers with larger water content (15 to 60 wt%). These fluctuations in the density of water distribution are presumed to be the precursors of the ~ 20 μm water pockets seen by Raman confocal imaging, and also give rise to 10-50 μm porous network seen in SEM. The surfaces of these polymers appeared to resist erosion while the core of the films continued to erode to form a porous structure. This could be due to differences in either the density of the polymer or the solvent environment in the bulk vs. the surface, or a combination of these two factors. There was no correlation between the rate of degradation and the amount of water uptake in these polymers, and this suggests that it is the bound-water and not the total amount of water that contributes to hydrolytic degradation.
- Published
- 2012
18. Confocal Raman Spectroscopy of Collagen Hydration: from Human Type I Collagen to Dermal Tissue
- Author
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Carol R. Flach, K. L. Andrew Chan, Richard Mendelsohn, David J. Moore, Guojin Zhang, Laurence Senak, Qihong Zhang, and Timothy Gillece
- Subjects
Hydrogen bond ,Oxide ,Analytical chemistry ,Biophysics ,chemistry.chemical_compound ,symbols.namesake ,medicine.anatomical_structure ,chemistry ,Deuterium ,Dermis ,symbols ,medicine ,Dynamic vapor sorption ,Raman spectroscopy ,Type I collagen ,Polyproline helix - Abstract
Collagen, representing approximately 75% of the dry weight of dermis, has a triple helical motif which consists of three polyproline II-like strands wrapped around a common axis. Studies of collagen's molecular and higher order structure have revealed the importance of water in stabilizing triple helical conformation and fiber assembly. A better understanding of collagen hydration is of interest to both medical and cosmetic industries. Confocal Raman spectroscopy, a noninvasive technique, has been used to measure the hydration properties of human Type I skin collagen and pigskin dermis at various relative humidity (RH) values. Raman spectra were also collected for Type I collagen and dermis samples upon exchange of a 100% RH H2O to deuterium oxide (D2O) environment. Changes observed in the Amide I and III spectral regions are consistent with modifications in hydrogen bonding as RH increased and H → D exchange took place. In particular, the relative intensity of the Raman peak at 938 cm−1, thought to arise from a protein backbone C-C stretching mode, was identified as a marker sensitive to collagen-bound water. Dynamic vapor sorption (DVS) measurements were also carried out on intact dermis to provide a quantitative measure of dermal hydration. The DVS results for internally absorbed water are compared with the Raman results and previous reports using a variety of physical techniques.
- Published
- 2011
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19. Raman Microscopy and Imaging: Applications to Skin Pharmacology and Wound Healing
- Author
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Carol R. Flach, Richard Mendelsohn, and Guojin Zhang
- Subjects
chemistry.chemical_classification ,medicine.medical_specialty ,integumentary system ,biology ,Confocal ,Skin pharmacology ,macromolecular substances ,Dermatology ,symbols.namesake ,medicine.anatomical_structure ,chemistry ,Keratin ,Microscopy ,biology.protein ,medicine ,Stratum corneum ,symbols ,Wound healing ,Raman spectroscopy ,Elastin ,Biomedical engineering - Abstract
The utility of confocal Raman microscopy to study biological events in skin is demonstrated with three examples. (i) monitoring the spatial and structural differences between native and cultured skin, (ii) tracking the permeation and biochemical transformation in skin of a Vitamin E derivative and (iii) tracking the spatial distribution of three major skin proteins (keratin, collagen, and elastin) during wound healing in an explant skin model.
- Published
- 2009
20. Descemet's Membrane Detachment Caused by the Improper Injection of Sodium Hyaluronate
- Author
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David S. Chu, Richard Mendelsohn, Guojin Zhang, and David Mostafavi
- Subjects
medicine.medical_specialty ,business.industry ,Sodium hyaluronate ,Glaucoma ,Surgical correction ,medicine.disease ,Descemet's membrane ,Sulfur hexafluoride ,chemistry.chemical_compound ,medicine.anatomical_structure ,chemistry ,Cornea ,Ophthalmology ,Medicine ,Tamponade ,Air bubble ,business - Abstract
A case of a Descemet's membrane detachment (DMD) caused by the inadvertent intracorneal injection of sodium hyaluronate was presented. This was concluded after chemical analysis of a viscous substance found in a patient's cornea showed to be a breakdown product of sodium hyaluronate. Surgical correction of the detachment included removing the viscous substance and tamponading the detachment with an air bubble. Although other gases such as sulfur hexafluoride (SF6) provide longer means of tamponade, they have increased postoperative risks like glaucoma associated with their use. Air can provide an effective means of tamponade with minimal postoperative risks.
- Published
- 2009
21. Imaging the prodrug-to-drug transformation of a 5-fluorouracil derivative in skin by confocal Raman microscopy
- Author
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Kenneth B. Sloan, Richard Mendelsohn, Guojin Zhang, Carol R. Flach, and David J. Moore
- Subjects
Drug ,Swine ,Confocal ,media_common.quotation_subject ,Dermatology ,Pharmacology ,Spectrum Analysis, Raman ,Biochemistry ,Permeability ,law.invention ,Confocal microscopy ,law ,Stratum corneum ,medicine ,Animals ,Prodrugs ,Molecular Biology ,Biotransformation ,media_common ,Transdermal ,Skin ,Microscopy, Confocal ,biology ,Epidermis (botany) ,Chemistry ,Cell Biology ,Prodrug ,medicine.anatomical_structure ,Enzyme inhibitor ,biology.protein ,Fluorouracil ,Epidermis - Abstract
The widespread adoption of transdermal drug delivery has been limited by the barrier properties of the outermost layer of the epidermis, the stratum corneum (SC). A variety of approaches have been developed to overcome the barrier, including the use of a prodrug form of an active therapeutic agent to enhance transdermal delivery. Once in the epidermis, the pro-molecule is converted to the active drug by endogenous enzymes or simple chemical hydrolysis. The prodrug selected for the current studies, 1-ethyloxycarbonyl-5-fluorouracil, is known to enhance transdermal delivery of 5-fluorouracil, an important systemic antitumor drug. Using confocal Raman microscopy on pigskin biopsies treated with prodrug, we are able to image the spatial distribution of both prodrug and drug in the SC and viable epidermis, thereby providing information about permeation and metabolism. This approach may readily be extended to a variety of dermatological processes.
- Published
- 2007
22. Measuring changes in chemistry, composition, and molecular structure within hair fibers by infrared and Raman spectroscopic imaging
- Author
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Guojin Zhang, Laurence Senak, and David J. Moore
- Subjects
Biomedical Engineering ,Infrared spectroscopy ,Spectrum Analysis, Raman ,law.invention ,Biomaterials ,symbols.namesake ,Optics ,Confocal microscopy ,law ,Spectroscopy, Fourier Transform Infrared ,Microscopy ,otorhinolaryngologic diseases ,Humans ,Protein secondary structure ,integumentary system ,Chemistry ,business.industry ,Molecular biophysics ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,Imaging spectroscopy ,symbols ,Biophysics ,sense organs ,Infrared microscopy ,Raman spectroscopy ,business ,Hair - Abstract
Spatially resolved infrared (IR) and Raman images are acquired from human hair cross sections or intact hair fibers. The full informational content of these spectra are spatially correlated to hair chemistry, anatomy, and structural organization through univariate and multivariate data analysis. Specific IR and Raman images from untreated human hair describing the spatial dependence of lipid and protein distribution, protein secondary structure, lipid chain conformational order, and distribution of disulfide cross-links in hair protein are presented in this study. Factor analysis of the image plane acquired with IR microscopy in hair sections, permits delineation of specific micro-regions within the hair. These data indicate that both IR and Raman imaging of molecular structural changes in a specific region of hair will prove to be valuable tools in the understanding of hair structure, physiology, and the effect of various stresses upon its integrity.
- Published
- 2011
23. Vibrational microscopy and imaging of skin: from single cells to intact tissue
- Author
-
Guojin Zhang, Carol R. Flach, David J. Moore, and Richard Mendelsohn
- Subjects
Keratinocytes ,Swine ,Confocal ,Infrared imaging ,Dermoscopy ,Absorption (skin) ,Spectrum Analysis, Raman ,Vibration ,Biochemistry ,Absorption ,Analytical Chemistry ,Nucleated cell ,Microscopy ,Keratin ,Spectroscopy, Fourier Transform Infrared ,medicine ,Animals ,Tissue Distribution ,Cells, Cultured ,Corneocytes ,Skin ,chemistry.chemical_classification ,Original Paper ,Corneocyte ,Microscopy, Confocal ,Confocal Raman ,medicine.anatomical_structure ,chemistry ,Phosphodiester bond ,Biophysics ,Solvents ,Protein secondary structure ,Feasibility Studies ,Keratins ,Epidermis - Abstract
Vibrational microscopy and imaging offer several advantages for a variety of dermatological applications, ranging from studies of isolated single cells (corneocytes) to characterization of endogenous components in intact tissue. Two applications are described to illustrate the power of these techniques for skin research. First, the feasibility of tracking structural alterations in the components of individual corneocytes is demonstrated. Two solvents, DMSO and chloroform/methanol, commonly used in dermatological research, are shown to induce large reversible alterations (alpha-helix to beta-sheet) in the secondary structure of keratin in isolated corneocytes. Second, factor analysis of image planes acquired with confocal Raman microscopy to a depth of 70 microm in intact pigskin, demonstrates the delineation of specific skin regions. Two particular components that are difficult to identify by other means were observed in the epidermis. One small region was formed from a conformationally ordered lipid phase containing cholesterol. In addition, the presence of nucleated cells in the tissue (most likely keratinocytes) was revealed by the spectral signatures of the phosphodiester and cytosine moieties of cellular DNA.
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